xref: /openbmc/linux/arch/arm/kernel/entry-common.S (revision 97da55fc) 
1/*
2 *  linux/arch/arm/kernel/entry-common.S
3 *
4 *  Copyright (C) 2000 Russell King
5 *
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License version 2 as
8 * published by the Free Software Foundation.
9 */
10
11#include <asm/unistd.h>
12#include <asm/ftrace.h>
13#include <asm/unwind.h>
14
15#ifdef CONFIG_NEED_RET_TO_USER
16#include <mach/entry-macro.S>
17#else
18	.macro  arch_ret_to_user, tmp1, tmp2
19	.endm
20#endif
21
22#include "entry-header.S"
23
24
25	.align	5
26/*
27 * This is the fast syscall return path.  We do as little as
28 * possible here, and this includes saving r0 back into the SVC
29 * stack.
30 */
31ret_fast_syscall:
32 UNWIND(.fnstart	)
33 UNWIND(.cantunwind	)
34	disable_irq				@ disable interrupts
35	ldr	r1, [tsk, #TI_FLAGS]
36	tst	r1, #_TIF_WORK_MASK
37	bne	fast_work_pending
38#if defined(CONFIG_IRQSOFF_TRACER)
39	asm_trace_hardirqs_on
40#endif
41
42	/* perform architecture specific actions before user return */
43	arch_ret_to_user r1, lr
44
45	restore_user_regs fast = 1, offset = S_OFF
46 UNWIND(.fnend		)
47
48/*
49 * Ok, we need to do extra processing, enter the slow path.
50 */
51fast_work_pending:
52	str	r0, [sp, #S_R0+S_OFF]!		@ returned r0
53work_pending:
54	mov	r0, sp				@ 'regs'
55	mov	r2, why				@ 'syscall'
56	bl	do_work_pending
57	cmp	r0, #0
58	beq	no_work_pending
59	movlt	scno, #(__NR_restart_syscall - __NR_SYSCALL_BASE)
60	ldmia	sp, {r0 - r6}			@ have to reload r0 - r6
61	b	local_restart			@ ... and off we go
62
63/*
64 * "slow" syscall return path.  "why" tells us if this was a real syscall.
65 */
66ENTRY(ret_to_user)
67ret_slow_syscall:
68	disable_irq				@ disable interrupts
69ENTRY(ret_to_user_from_irq)
70	ldr	r1, [tsk, #TI_FLAGS]
71	tst	r1, #_TIF_WORK_MASK
72	bne	work_pending
73no_work_pending:
74#if defined(CONFIG_IRQSOFF_TRACER)
75	asm_trace_hardirqs_on
76#endif
77	/* perform architecture specific actions before user return */
78	arch_ret_to_user r1, lr
79
80	restore_user_regs fast = 0, offset = 0
81ENDPROC(ret_to_user_from_irq)
82ENDPROC(ret_to_user)
83
84/*
85 * This is how we return from a fork.
86 */
87ENTRY(ret_from_fork)
88	bl	schedule_tail
89	cmp	r5, #0
90	movne	r0, r4
91	adrne	lr, BSYM(1f)
92	movne	pc, r5
931:	get_thread_info tsk
94	b	ret_slow_syscall
95ENDPROC(ret_from_fork)
96
97	.equ NR_syscalls,0
98#define CALL(x) .equ NR_syscalls,NR_syscalls+1
99#include "calls.S"
100
101/*
102 * Ensure that the system call table is equal to __NR_syscalls,
103 * which is the value the rest of the system sees
104 */
105.ifne NR_syscalls - __NR_syscalls
106.error "__NR_syscalls is not equal to the size of the syscall table"
107.endif
108
109#undef CALL
110#define CALL(x) .long x
111
112#ifdef CONFIG_FUNCTION_TRACER
113/*
114 * When compiling with -pg, gcc inserts a call to the mcount routine at the
115 * start of every function.  In mcount, apart from the function's address (in
116 * lr), we need to get hold of the function's caller's address.
117 *
118 * Older GCCs (pre-4.4) inserted a call to a routine called mcount like this:
119 *
120 *	bl	mcount
121 *
122 * These versions have the limitation that in order for the mcount routine to
123 * be able to determine the function's caller's address, an APCS-style frame
124 * pointer (which is set up with something like the code below) is required.
125 *
126 *	mov     ip, sp
127 *	push    {fp, ip, lr, pc}
128 *	sub     fp, ip, #4
129 *
130 * With EABI, these frame pointers are not available unless -mapcs-frame is
131 * specified, and if building as Thumb-2, not even then.
132 *
133 * Newer GCCs (4.4+) solve this problem by introducing a new version of mcount,
134 * with call sites like:
135 *
136 *	push	{lr}
137 *	bl	__gnu_mcount_nc
138 *
139 * With these compilers, frame pointers are not necessary.
140 *
141 * mcount can be thought of as a function called in the middle of a subroutine
142 * call.  As such, it needs to be transparent for both the caller and the
143 * callee: the original lr needs to be restored when leaving mcount, and no
144 * registers should be clobbered.  (In the __gnu_mcount_nc implementation, we
145 * clobber the ip register.  This is OK because the ARM calling convention
146 * allows it to be clobbered in subroutines and doesn't use it to hold
147 * parameters.)
148 *
149 * When using dynamic ftrace, we patch out the mcount call by a "mov r0, r0"
150 * for the mcount case, and a "pop {lr}" for the __gnu_mcount_nc case (see
151 * arch/arm/kernel/ftrace.c).
152 */
153
154#ifndef CONFIG_OLD_MCOUNT
155#if (__GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 4))
156#error Ftrace requires CONFIG_FRAME_POINTER=y with GCC older than 4.4.0.
157#endif
158#endif
159
160.macro mcount_adjust_addr rd, rn
161	bic	\rd, \rn, #1		@ clear the Thumb bit if present
162	sub	\rd, \rd, #MCOUNT_INSN_SIZE
163.endm
164
165.macro __mcount suffix
166	mcount_enter
167	ldr	r0, =ftrace_trace_function
168	ldr	r2, [r0]
169	adr	r0, .Lftrace_stub
170	cmp	r0, r2
171	bne	1f
172
173#ifdef CONFIG_FUNCTION_GRAPH_TRACER
174	ldr     r1, =ftrace_graph_return
175	ldr     r2, [r1]
176	cmp     r0, r2
177	bne     ftrace_graph_caller\suffix
178
179	ldr     r1, =ftrace_graph_entry
180	ldr     r2, [r1]
181	ldr     r0, =ftrace_graph_entry_stub
182	cmp     r0, r2
183	bne     ftrace_graph_caller\suffix
184#endif
185
186	mcount_exit
187
1881: 	mcount_get_lr	r1			@ lr of instrumented func
189	mcount_adjust_addr	r0, lr		@ instrumented function
190	adr	lr, BSYM(2f)
191	mov	pc, r2
1922:	mcount_exit
193.endm
194
195.macro __ftrace_caller suffix
196	mcount_enter
197
198	mcount_get_lr	r1			@ lr of instrumented func
199	mcount_adjust_addr	r0, lr		@ instrumented function
200
201	.globl ftrace_call\suffix
202ftrace_call\suffix:
203	bl	ftrace_stub
204
205#ifdef CONFIG_FUNCTION_GRAPH_TRACER
206	.globl ftrace_graph_call\suffix
207ftrace_graph_call\suffix:
208	mov	r0, r0
209#endif
210
211	mcount_exit
212.endm
213
214.macro __ftrace_graph_caller
215	sub	r0, fp, #4		@ &lr of instrumented routine (&parent)
216#ifdef CONFIG_DYNAMIC_FTRACE
217	@ called from __ftrace_caller, saved in mcount_enter
218	ldr	r1, [sp, #16]		@ instrumented routine (func)
219	mcount_adjust_addr	r1, r1
220#else
221	@ called from __mcount, untouched in lr
222	mcount_adjust_addr	r1, lr	@ instrumented routine (func)
223#endif
224	mov	r2, fp			@ frame pointer
225	bl	prepare_ftrace_return
226	mcount_exit
227.endm
228
229#ifdef CONFIG_OLD_MCOUNT
230/*
231 * mcount
232 */
233
234.macro mcount_enter
235	stmdb	sp!, {r0-r3, lr}
236.endm
237
238.macro mcount_get_lr reg
239	ldr	\reg, [fp, #-4]
240.endm
241
242.macro mcount_exit
243	ldr	lr, [fp, #-4]
244	ldmia	sp!, {r0-r3, pc}
245.endm
246
247ENTRY(mcount)
248#ifdef CONFIG_DYNAMIC_FTRACE
249	stmdb	sp!, {lr}
250	ldr	lr, [fp, #-4]
251	ldmia	sp!, {pc}
252#else
253	__mcount _old
254#endif
255ENDPROC(mcount)
256
257#ifdef CONFIG_DYNAMIC_FTRACE
258ENTRY(ftrace_caller_old)
259	__ftrace_caller _old
260ENDPROC(ftrace_caller_old)
261#endif
262
263#ifdef CONFIG_FUNCTION_GRAPH_TRACER
264ENTRY(ftrace_graph_caller_old)
265	__ftrace_graph_caller
266ENDPROC(ftrace_graph_caller_old)
267#endif
268
269.purgem mcount_enter
270.purgem mcount_get_lr
271.purgem mcount_exit
272#endif
273
274/*
275 * __gnu_mcount_nc
276 */
277
278.macro mcount_enter
279	stmdb	sp!, {r0-r3, lr}
280.endm
281
282.macro mcount_get_lr reg
283	ldr	\reg, [sp, #20]
284.endm
285
286.macro mcount_exit
287	ldmia	sp!, {r0-r3, ip, lr}
288	mov	pc, ip
289.endm
290
291ENTRY(__gnu_mcount_nc)
292#ifdef CONFIG_DYNAMIC_FTRACE
293	mov	ip, lr
294	ldmia	sp!, {lr}
295	mov	pc, ip
296#else
297	__mcount
298#endif
299ENDPROC(__gnu_mcount_nc)
300
301#ifdef CONFIG_DYNAMIC_FTRACE
302ENTRY(ftrace_caller)
303	__ftrace_caller
304ENDPROC(ftrace_caller)
305#endif
306
307#ifdef CONFIG_FUNCTION_GRAPH_TRACER
308ENTRY(ftrace_graph_caller)
309	__ftrace_graph_caller
310ENDPROC(ftrace_graph_caller)
311#endif
312
313.purgem mcount_enter
314.purgem mcount_get_lr
315.purgem mcount_exit
316
317#ifdef CONFIG_FUNCTION_GRAPH_TRACER
318	.globl return_to_handler
319return_to_handler:
320	stmdb	sp!, {r0-r3}
321	mov	r0, fp			@ frame pointer
322	bl	ftrace_return_to_handler
323	mov	lr, r0			@ r0 has real ret addr
324	ldmia	sp!, {r0-r3}
325	mov	pc, lr
326#endif
327
328ENTRY(ftrace_stub)
329.Lftrace_stub:
330	mov	pc, lr
331ENDPROC(ftrace_stub)
332
333#endif /* CONFIG_FUNCTION_TRACER */
334
335/*=============================================================================
336 * SWI handler
337 *-----------------------------------------------------------------------------
338 */
339
340	.align	5
341ENTRY(vector_swi)
342	sub	sp, sp, #S_FRAME_SIZE
343	stmia	sp, {r0 - r12}			@ Calling r0 - r12
344 ARM(	add	r8, sp, #S_PC		)
345 ARM(	stmdb	r8, {sp, lr}^		)	@ Calling sp, lr
346 THUMB(	mov	r8, sp			)
347 THUMB(	store_user_sp_lr r8, r10, S_SP	)	@ calling sp, lr
348	mrs	r8, spsr			@ called from non-FIQ mode, so ok.
349	str	lr, [sp, #S_PC]			@ Save calling PC
350	str	r8, [sp, #S_PSR]		@ Save CPSR
351	str	r0, [sp, #S_OLD_R0]		@ Save OLD_R0
352	zero_fp
353
354	/*
355	 * Get the system call number.
356	 */
357
358#if defined(CONFIG_OABI_COMPAT)
359
360	/*
361	 * If we have CONFIG_OABI_COMPAT then we need to look at the swi
362	 * value to determine if it is an EABI or an old ABI call.
363	 */
364#ifdef CONFIG_ARM_THUMB
365	tst	r8, #PSR_T_BIT
366	movne	r10, #0				@ no thumb OABI emulation
367	ldreq	r10, [lr, #-4]			@ get SWI instruction
368#else
369	ldr	r10, [lr, #-4]			@ get SWI instruction
370#endif
371#ifdef CONFIG_CPU_ENDIAN_BE8
372	rev	r10, r10			@ little endian instruction
373#endif
374
375#elif defined(CONFIG_AEABI)
376
377	/*
378	 * Pure EABI user space always put syscall number into scno (r7).
379	 */
380#elif defined(CONFIG_ARM_THUMB)
381	/* Legacy ABI only, possibly thumb mode. */
382	tst	r8, #PSR_T_BIT			@ this is SPSR from save_user_regs
383	addne	scno, r7, #__NR_SYSCALL_BASE	@ put OS number in
384	ldreq	scno, [lr, #-4]
385
386#else
387	/* Legacy ABI only. */
388	ldr	scno, [lr, #-4]			@ get SWI instruction
389#endif
390
391#ifdef CONFIG_ALIGNMENT_TRAP
392	ldr	ip, __cr_alignment
393	ldr	ip, [ip]
394	mcr	p15, 0, ip, c1, c0		@ update control register
395#endif
396	enable_irq
397
398	get_thread_info tsk
399	adr	tbl, sys_call_table		@ load syscall table pointer
400
401#if defined(CONFIG_OABI_COMPAT)
402	/*
403	 * If the swi argument is zero, this is an EABI call and we do nothing.
404	 *
405	 * If this is an old ABI call, get the syscall number into scno and
406	 * get the old ABI syscall table address.
407	 */
408	bics	r10, r10, #0xff000000
409	eorne	scno, r10, #__NR_OABI_SYSCALL_BASE
410	ldrne	tbl, =sys_oabi_call_table
411#elif !defined(CONFIG_AEABI)
412	bic	scno, scno, #0xff000000		@ mask off SWI op-code
413	eor	scno, scno, #__NR_SYSCALL_BASE	@ check OS number
414#endif
415
416local_restart:
417	ldr	r10, [tsk, #TI_FLAGS]		@ check for syscall tracing
418	stmdb	sp!, {r4, r5}			@ push fifth and sixth args
419
420	tst	r10, #_TIF_SYSCALL_WORK		@ are we tracing syscalls?
421	bne	__sys_trace
422
423	cmp	scno, #NR_syscalls		@ check upper syscall limit
424	adr	lr, BSYM(ret_fast_syscall)	@ return address
425	ldrcc	pc, [tbl, scno, lsl #2]		@ call sys_* routine
426
427	add	r1, sp, #S_OFF
4282:	mov	why, #0				@ no longer a real syscall
429	cmp	scno, #(__ARM_NR_BASE - __NR_SYSCALL_BASE)
430	eor	r0, scno, #__NR_SYSCALL_BASE	@ put OS number back
431	bcs	arm_syscall
432	b	sys_ni_syscall			@ not private func
433ENDPROC(vector_swi)
434
435	/*
436	 * This is the really slow path.  We're going to be doing
437	 * context switches, and waiting for our parent to respond.
438	 */
439__sys_trace:
440	mov	r1, scno
441	add	r0, sp, #S_OFF
442	bl	syscall_trace_enter
443
444	adr	lr, BSYM(__sys_trace_return)	@ return address
445	mov	scno, r0			@ syscall number (possibly new)
446	add	r1, sp, #S_R0 + S_OFF		@ pointer to regs
447	cmp	scno, #NR_syscalls		@ check upper syscall limit
448	ldmccia	r1, {r0 - r6}			@ have to reload r0 - r6
449	stmccia	sp, {r4, r5}			@ and update the stack args
450	ldrcc	pc, [tbl, scno, lsl #2]		@ call sys_* routine
451	cmp	scno, #-1			@ skip the syscall?
452	bne	2b
453	add	sp, sp, #S_OFF			@ restore stack
454	b	ret_slow_syscall
455
456__sys_trace_return:
457	str	r0, [sp, #S_R0 + S_OFF]!	@ save returned r0
458	mov	r0, sp
459	bl	syscall_trace_exit
460	b	ret_slow_syscall
461
462	.align	5
463#ifdef CONFIG_ALIGNMENT_TRAP
464	.type	__cr_alignment, #object
465__cr_alignment:
466	.word	cr_alignment
467#endif
468	.ltorg
469
470/*
471 * This is the syscall table declaration for native ABI syscalls.
472 * With EABI a couple syscalls are obsolete and defined as sys_ni_syscall.
473 */
474#define ABI(native, compat) native
475#ifdef CONFIG_AEABI
476#define OBSOLETE(syscall) sys_ni_syscall
477#else
478#define OBSOLETE(syscall) syscall
479#endif
480
481	.type	sys_call_table, #object
482ENTRY(sys_call_table)
483#include "calls.S"
484#undef ABI
485#undef OBSOLETE
486
487/*============================================================================
488 * Special system call wrappers
489 */
490@ r0 = syscall number
491@ r8 = syscall table
492sys_syscall:
493		bic	scno, r0, #__NR_OABI_SYSCALL_BASE
494		cmp	scno, #__NR_syscall - __NR_SYSCALL_BASE
495		cmpne	scno, #NR_syscalls	@ check range
496		stmloia	sp, {r5, r6}		@ shuffle args
497		movlo	r0, r1
498		movlo	r1, r2
499		movlo	r2, r3
500		movlo	r3, r4
501		ldrlo	pc, [tbl, scno, lsl #2]
502		b	sys_ni_syscall
503ENDPROC(sys_syscall)
504
505sys_sigreturn_wrapper:
506		add	r0, sp, #S_OFF
507		mov	why, #0		@ prevent syscall restart handling
508		b	sys_sigreturn
509ENDPROC(sys_sigreturn_wrapper)
510
511sys_rt_sigreturn_wrapper:
512		add	r0, sp, #S_OFF
513		mov	why, #0		@ prevent syscall restart handling
514		b	sys_rt_sigreturn
515ENDPROC(sys_rt_sigreturn_wrapper)
516
517sys_statfs64_wrapper:
518		teq	r1, #88
519		moveq	r1, #84
520		b	sys_statfs64
521ENDPROC(sys_statfs64_wrapper)
522
523sys_fstatfs64_wrapper:
524		teq	r1, #88
525		moveq	r1, #84
526		b	sys_fstatfs64
527ENDPROC(sys_fstatfs64_wrapper)
528
529/*
530 * Note: off_4k (r5) is always units of 4K.  If we can't do the requested
531 * offset, we return EINVAL.
532 */
533sys_mmap2:
534#if PAGE_SHIFT > 12
535		tst	r5, #PGOFF_MASK
536		moveq	r5, r5, lsr #PAGE_SHIFT - 12
537		streq	r5, [sp, #4]
538		beq	sys_mmap_pgoff
539		mov	r0, #-EINVAL
540		mov	pc, lr
541#else
542		str	r5, [sp, #4]
543		b	sys_mmap_pgoff
544#endif
545ENDPROC(sys_mmap2)
546
547#ifdef CONFIG_OABI_COMPAT
548
549/*
550 * These are syscalls with argument register differences
551 */
552
553sys_oabi_pread64:
554		stmia	sp, {r3, r4}
555		b	sys_pread64
556ENDPROC(sys_oabi_pread64)
557
558sys_oabi_pwrite64:
559		stmia	sp, {r3, r4}
560		b	sys_pwrite64
561ENDPROC(sys_oabi_pwrite64)
562
563sys_oabi_truncate64:
564		mov	r3, r2
565		mov	r2, r1
566		b	sys_truncate64
567ENDPROC(sys_oabi_truncate64)
568
569sys_oabi_ftruncate64:
570		mov	r3, r2
571		mov	r2, r1
572		b	sys_ftruncate64
573ENDPROC(sys_oabi_ftruncate64)
574
575sys_oabi_readahead:
576		str	r3, [sp]
577		mov	r3, r2
578		mov	r2, r1
579		b	sys_readahead
580ENDPROC(sys_oabi_readahead)
581
582/*
583 * Let's declare a second syscall table for old ABI binaries
584 * using the compatibility syscall entries.
585 */
586#define ABI(native, compat) compat
587#define OBSOLETE(syscall) syscall
588
589	.type	sys_oabi_call_table, #object
590ENTRY(sys_oabi_call_table)
591#include "calls.S"
592#undef ABI
593#undef OBSOLETE
594
595#endif
596
597